The subject matter disclosed herein relates generally to power supplies, and more particularly to step-up voltage converter power supplies.
Conventional voltage converter devices, particularly DC to DC converter devices, generally include switching circuits and/or charge-pumps. Additionally or alternatively, flyback inductors may be used in the voltage converter devices. These components in the converter devices create high transient currents that generate both radiated and conducted Electromagnetic Interference (EMI). As a result of the generated EMI, these converter devices are not suitable for some applications, such as magnetic field applications (e.g., Magnetic Resonance Imaging (MRI) applications) where the EMI performance can affect imaging operations and imaging quality, and therefore, are unacceptable. In other applications having low EMI requirements, including lower level signal switching applications (e.g., low noise upconverters, RF signal routing, etc.), these conventional voltage converter devices can also cause adverse affects.
Shielding and filtering are often used to reduce EMI, for example, providing shielding in connection with charge pumps. However, the shielding or filtering often has limited effectiveness and can have adverse affects in some applications, such as distorting magnetic and RF field homogeneity. Air core transformer techniques are also used. However, even with resonant primary and secondary circuits, these transformers have low efficiency and the large currents generate EMI. Other AC to DC power supplies are known that generate power outside a noise sensitive area and send the power into the noise sensitive area. However, high voltage interfaces are required in these systems, which can have electrical isolation and leakage current issues that can lead to patient safety concerns.
Power supplies providing step-up voltage conversion are also known and that include piezoelectric transformers, such as LCD backlight power supplies. However, these power supplies use high current switching and magnetic devices. These high current switching and magnetic components can have adverse affects in certain applications, for example, magnetic field applications.